Showing papers by "Barbara E. Murray published in 1991"
TL;DR: It is concluded that pulsed-field gel electrophoresis of DNA digested with low-frequency-cleavage restriction enzymes offers a relatively simple method of comparing E. faecium from six different geographic locations for the purpose of epidemiologic study.
Abstract: Pulsed-field gel electrophoresis was used to compare 34 isolates of Enterococcus faecium from six different geographic locations. This procedure generated an average of 13 discernible fragment bands per isolate (range, 10 to 19 fragment bands) of 34 to 485 kb. The resulting restriction endonuclease digestion patterns were quite heterogeneous and were able to differentiate 27 of 34 isolates from each other, as defined by one or more mismatched fragment bands. Five patterns were shared by two or more isolates, and each set of isolates with matching patterns (shared pattern) originated in the same medical center, suggesting a common epidemiologic background, including highly penicillin resistant isolates in Richmond and Philadelphia. We conclude that pulsed-field gel electrophoresis of DNA digested with low-frequency-cleavage restriction enzymes offers a relatively simple method of comparing E. faecium for the purpose of epidemiologic study.
166 citations
TL;DR: The selective pressure generated by the use of antimicrobial agents, together with the ability of bacteria to acquire and spread resistance and the capacity of humans to transmit bacteria, suggest that antimicrobial resistance will continue to be a problem for the foreseeable future.
Abstract: Emergence of resistance to antimicrobial agents among previously susceptible organisms continues to be an important obstacle to the successful treatment of bacterial infections. In hospitals, plasmid-mediated resistance to third-generation cephalosporins and monobactams has recently appeared in gram-negative bacilli, due primarily to mutations in TEM- and SHV-type enzymes. Among nosocomial enterococci, vancomycin resistance, beta-lactamase production, and high-level resistance to all aminoglycosides have recently been added to this organism's already formidable armamentarium of resistance properties. Also, resistance to fluoroquinolones and rifampin has been emerging in methicillin-resistant Staphylococcus aureus. In the community, organisms in which resistance plays a particularly important role are shigellae, Haemophilus influenzae, gonococci, and pneumococci, particularly in developing countries. beta-lactamase-producing meningococci have been reported for the first time. The selective pressure generated by the use of antimicrobial agents, together with the ability of bacteria to acquire and spread resistance and the capacity of humans to transmit bacteria, suggest that antimicrobial resistance will continue to be a problem for the foreseeable future.
155 citations
TL;DR: In Enterococcus faecalis, the genetic determinant encoding gentamicin resistance on the conjugative plasmid pBEM10 previously has been shown to be on a mobile element that was shown to relocate in the absence of homologous recombination, and this element, termed Tn5281, was shows to be similar to the Gmr transposons found in Australian isolates of Staphylococcus aureus and Tn4031.
Abstract: In Enterococcus faecalis, the genetic determinant encoding gentamicin resistance (Gmr) on the conjugative plasmid pBEM10 previously has been shown to be on a mobile element. In the current study, this element, termed Tn5281, was shown to relocate in the absence of homologous recombination in E. faecalis UV202. On the basis of restriction endonuclease analysis and DNA-DNA hybridization studies, Tn5281 was shown to be similar, if not identical, to the Gmr transposons Tn4001 found in Australian isolates of Staphylococcus aureus and Tn4031 found in U.S. isolates of Staphylococcus epidermidis, since all three of these transposons have symmetrically located HindIII (2.5 kb apart), ClaI (slightly more than 2.5 kb apart), and HaeIII (3.9 kb apart) sites. Restriction endonuclease digestion patterns of Tn5281 generated with HincII, ScaI, and AluI were also consistent with Tn4001 and Tn4031. By using a probe specific for the external portion of the terminal inverted repeat of Tn4031, it was determined that each terminus of Tn5281 contained a 0.35-kb HaeIII fragment and a 0.7-kb HindIII-HaeIII fragment. The sizes of these fragments are identical to those found in the staphylococcal transposons, which is a further indication that inverted repeats like IS256 are present in Tn5281. A 1-kb HaeIII fragment in pBEM10 also hybridized with this probe, which indicates that Tn5281 in pBEM10 contains a double copy of the inverted repeat at one end.
110 citations
TL;DR: The nucleotide sequence of the constitutively produced beta-lactamase (Bla) gene from Enterococcus faecalis HH22 was shown to be identical to the published sequences of three of four staphylococcal type A beta- lactam enzyme genes; more differences were seen with the genes for staphymic type C and D enzymes.
Abstract: The nucleotide sequence of the constitutively produced beta-lactamase (Bla) gene from Enterococcus faecalis HH22 was shown to be identical to the published sequences of three of four staphylococcal type A beta-lactamase genes; more differences were seen with the genes for staphylococcal type C and D enzymes One hundred forty nucleotides upstream of the beta-lactamase start codon were determined for an inducible staphylococcal beta-lactamase and were identical to those of the constitutively expressed enterococcal gene, indicating that the changes resulting in constitutive expression are not due to changes in the promoter or operator region Moreover, complementation studies indicated that production of the enterococcal enzyme could be repressed The genes for the enterococcal Bla and an inducible staphylococcal Bla were each cloned into a shuttle vector and transformed into enterococcal and staphylococcal recipients The major difference between the backgrounds of the two hosts was that more enzyme was produced by the staphylococcal host, regardless of the source of the gene The location of the enzyme was found to be host dependent, since each cloned gene generated extracellular (free) enzyme in the staphylococcus and cell-bound enzyme in the enterococcus On the basis of the identities of the enterococcal Bla and several staphylococcal Bla sequences, these data suggest the recent spread of beta-lactamase to enterococci and also suggest the loss of a functional repressor
37 citations
TL;DR: These data show that household contacts of children with hemolytic uremic syndrome are commonly colonized with Shiga-like toxin-producing E. coli and seroconversion to Shigo toxin-like toxins occurs frequently in family members ofChildren with Hemolytic Uremic Syndrome.
Abstract: We conducted a prospective study in 87 household contacts of 51 children with hemolytic uremic syndrome to determine the frequency of infection with Shiga-like toxin-producing bacteria. Gastrointestinal tract symptoms occurred in only 1 of 87 contacts. Free fecal toxin was detected in 25 of 64 (39%) of the household members. Neutralization with specific antisera to Shiga-like toxins I and II (SLT-I, SLT-II) revealed that in 6 of these household contacts only SLT-I was present in stool, in 10 only SLT-II was present and in 9 both toxins were found. Thirty-three percent of the hemolytic uremic syndrome families in which 2 or more members were studied had more than 1 household member with free fecal toxin in stool. None of the household contacts was found to have E. coli O157:H7 in feces. Serum samples were available in 77 household contacts; 75% (58 of 77) had serum neutralizing titers of greater than or equal to 1:4 to 1 or both toxins. In those contacts for whom paired sera were available, seroconversion was found in 10 of 24 (42%). These data show that household contacts of children with hemolytic uremic syndrome are commonly colonized with Shiga-like toxin-producing E. coli and seroconversion to Shiga-like toxins occurs frequently in family members of children with hemolytic uremic syndrome.
33 citations
TL;DR: Acquisition of resistance to TMP is another example of the multiple antimicrobial resistance typically displayed by enterococci.
Abstract: Multiresistant enterococci were tested for susceptibility to trimethoprim (TMP). Although most enterococci are inhibited by less than or equal to 1.0 microgram/ml, the MICs for 7 of 29 selected multiresistant isolates were greater than or equal to 8 micrograms/ml, including for two beta-lactamase positive (Bla+) strains, for which the MICs of TMP were greater than 1,000 micrograms/ml, and for another Bla+ strain, for which the MIC was 128 micrograms/ml. None of five isolates tested transferred TMP resistance and none of the resistant isolates hybridized to the dfrA gene of Staphylococcus aureus. Whether TMP resistance in enterococci is due to a mutation(s) or to acquisition of a new gene is not known. Acquisition of resistance to TMP is another example of the multiple antimicrobial resistance typically displayed by enterococci.
9 citations